Spacers for ion-exchange device

ABSTRACT

Provided are spacers, ion-exchange devices comprising spacers, and methods of preparing spacers for improved fluid distribution and sealing throughout an ion-exchange device. These spacers can include an internal cavity surrounded by a perimeter of the spacer. The perimeter can have a first opening and a second opening within the perimeter, and the first opening and the second opening can be located on opposite sides of the internal cavity. The spacers can also have a first and second plurality of channels located within the perimeter, wherein each channel of the first and second plurality of channels extends from the internal cavity towards the first opening or the second opening.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/685,617, filed Nov. 15, 2019, which claims the benefit of U.S.Provisional Application No. 62/768,644, filed Nov. 16, 2018, the entirecontents of both of which are incorporated herein by reference.

FIELD OF THE DISCLOSURE

This disclosure relates to spacers for a membrane-based desalinationdevice. More particularly, this disclosure relates to spacers forimproved flow distribution through an intermembrane chamber and acrossan ion-exchange membrane of an ion-exchange device, as well as improvedexternal and internal seals of an ion-exchange device.

BACKGROUND OF THE DISCLOSURE

Electrodialysis is one example of a membrane-based large scaledesalination method. Specifically, electrodialysis can be used in anion-exchange device to selectively remove positive and negative ionsfrom a water source (e.g., brackish water or brine solution produced inreverse osmosis units) by transporting salt ions from one solution toanother by way of ion-exchange membranes. For optimal performance, anion-exchange device employing electrodialysis utilizes an electricalcurrent to separate charged ions from the water flowing through thedevice. For example, an ion-exchange device can include a pair ofelectrodes, alternating anionic and cationic exchange membranes, andspacers. A voltage can be applied to one or more of the electrodes toinitiate an electrochemical reaction. The alternating cationic exchangemembranes and anionic exchange membranes can selectively remove ionsfrom a first stream of fluid while introducing the removed ions to anadjacent, second stream of fluid.

The spacers of an ion-exchange device can be placed between thealternating ion-exchange membranes. Spacers are used to createseparation between ion-exchange membranes and form intermembranechambers, which allow the passage of fluid. Spacers are also used toform internal seals between adjacent intermembrane chambers of thedevice and external seals to protect the fluid flowing through thedevice from the external environment.

Some ion-exchange devices may include additional components to help sealthe device. For example, sealing components may include adhesives,o-rings, and/or mechanical seals.

SUMMARY OF THE DISCLOSURE

Provided are improved spacer borders and methods for preparing improvedspacer borders for use in a membrane-based desalination device.Particularly, the devices, methods, and techniques provided are forspacer borders that have improved sealing characteristics and enableimproved fluid distribution across an ion-exchange membrane (i.e.,cationic-exchange membranes (“CEMs”) and anionic-exchange membranes(“AEMs”)).

Spacer borders and methods of fabricating spacer borders provided hereincan provide improved external seals along the outside of an ion-exchangedevice and improved internal seals along adjacent intermembrane chamberswithin an ion-exchange device. Specifically, improved external seals canmaximize hydraulic recovery, minimize safety hazards to operators, andprotect the fluid flowing through the ion-exchange device from theexternal environment. Improved internal seals can minimizecross-contamination from one intermembrane chamber to another and canmaximize production rates. Improved flow distribution can maximize theeffective area of charge transfer on an ion-exchange membrane surfaceand the capacity of the ion-exchange device. Accordingly, spacer bordersand methods for preparing spacer borders for ion-exchange devicesprovided herein can maximize: hydraulic recovery, production rates, theeffective area of charge transfer on an ion-exchange membrane surface,and the capacity of the ion-exchange device; and can minimize: safetyhazards and cross-contamination.

Unlike the sealing components mentioned above (i.e., adhesives, o-rings,and mechanical seals), spacer borders disclosed herein can be moreeffective, more reliable, and use less component parts. Specifically,many adhesives suitable for sealing an ion-exchange device suffer due torepeated swelling and shrinking of the ion-exchange membranes caused byenvironmental conditions and water quality. This swelling and shrinkingof an ion-exchange membrane weakens the seal over time and ultimatelycreates leaks throughout the system. O-rings inherently add anadditional mechanical component and thus an additional degree ofcomplexity. This additional component and increased complexity canintroduce misalignment problems in a membrane stack of an ion-exchangedevice. And finally, mechanical seals require a significant compressionforce to seal the flat surfaces of the spacer borders against a surfaceof an ion-exchange membrane. Accordingly, improved spacer borders andmethods for preparing improved spacer borders provided herein canminimize water permeability of the membrane, can minimize the number ofadditional component parts, and can minimize the compression forcerequired to seal components of the device.

One type of spacer border for use in an ion-exchange device includes aninternal cavity filled with fabric or mesh. Spacer borders of thisconfiguration provide support to the ion-exchange membranes across alength of the device and can provide more reliable external and internalseals throughout the device.

In some embodiments, a spacer for an ion-exchange device is provided,the spacer comprising: a spacer mesh; and a spacer border comprising: aninternal cavity surrounded by a perimeter of the spacer border; a firstopening and a second opening within the perimeter of the spacer border,wherein the first opening and the second opening are located on oppositesides of the internal cavity; a first plurality of channels locatedwithin the perimeter and between the first opening and the internalcavity, wherein each channel of the first plurality of channels extendsfrom the internal cavity towards the first opening; and a secondplurality of channels located within the perimeter and between thesecond opening and the internal cavity, wherein each channel of thesecond plurality of channels extends from the internal cavity towardsthe second opening.

In some embodiments of the spacer, the spacer border comprises a polymerhaving a stiffness greater than 2.5 GPa.

In some embodiments of the spacer, the spacer border comprisespolyethylene terephthalate.

In some embodiments of the spacer, each channel of the first pluralityof channels and each channel of the second plurality of channelscomprises a width from 0.005 inches to 0.015 inches.

In some embodiments of the spacer, the first plurality of channels isoriented in a first array configuration and the second plurality ofchannels is oriented in a second array configuration.

In some embodiments of the spacer, the spacer comprises a thickness of0.003 inches to 0.020 inches.

In some embodiments of the spacer, the spacer comprises a thickness of0.003 inches to 0.010 inches.

In some embodiments of the spacer, an end of each channel of the firstplurality of channels and an end of each channel of the second pluralityof channels opens into the internal cavity.

In some embodiments of the spacer, the first array configuration isspatially related to the second array configuration such that the firstarray configuration is a 180° rotation of the second array configurationwith respect to a central location of the spacer.

In some embodiments of the spacer, the spacer mesh and the spacer borderare integral.

In some embodiments of the spacer, the spacer mesh and the spacer borderare separate components.

In some embodiments, an ion-exchange device is provided, theion-exchange device comprising: a first electrode; a firstcationic-exchange membrane; a first intermembrane chamber comprising afirst spacer border, the first spacer border comprising a first internalcavity, a first opening, and a first plurality of channels; a firstanionic-exchange membrane; a intermembrane chamber comprising a secondspacer border, the second spacer border comprising a second internalcavity, a second opening, and a second plurality of channels; a secondcationic-exchange membrane; and a second electrode, wherein the firstelectrode, the first cationic-exchange membrane, the first spacer, thefirst anionic-exchange membrane, the second spacer, the secondcationic-exchange membrane, and the second electrode are sandwichedbetween a pair of compression plates, and wherein the first plurality ofchannels is located between the first opening and the first internalcavity of the first spacer border, wherein each channel of the firstplurality of channels extends from the first internal cavity towards thefirst opening, and the second plurality of channels is located betweenthe second opening and the second internal cavity of the second spacerborder, wherein each channel of the second plurality of channels extendsfrom the second internal cavity towards the second opening of the secondspacer border.

In some embodiments of the ion-exchange device, the first spacer borderand the second spacer border comprise a polymer having a stiffnessgreater than 2.5 GPa.

In some embodiments of the ion-exchange device, the first spacer borderand the second spacer border comprise polyethylene terephthalate.

In some embodiments of the ion-exchange device, the channels of thefirst plurality of channels and the channels of the second plurality ofchannels each comprise a width of 0.005 inches to 0.015 inches.

In some embodiments of the ion-exchange device, the first spacer and thesecond spacer each comprise a thickness of 0.003 inches to 0.020 inches.

In some embodiments of the ion-exchange device, the first spacer and thesecond spacer each comprise a thickness of 0.003 inches to 0.010 inches.

In some embodiments of the ion-exchange device, the firstcationic-exchange membrane, the first anionic-exchange membrane, and thesecond cationic-exchange membrane comprise a thickness equal to or lessthan 0.020 inches.

In some embodiments of the ion-exchange device, the first plurality ofchannels are arranged in a first array configuration and the secondplurality of channels are arranged in a second array configuration.

In some embodiments of the ion-exchange device, the channels of thefirst plurality of channels of the first array configuration extend froman inlet opening radially outward towards the first internal cavity ofthe first spacer border.

In some embodiments of the ion-exchange device, the first spacercomprises a third opening, a third plurality of channels, and a thirdarray configuration, wherein the channels of the third plurality ofchannels of the third array configuration extend from the first internalcavity radially inward towards the third opening of the first spacerborder.

In some embodiments of the ion-exchange device, the first arrayconfiguration is spatially related to the third array configuration suchthat the first array configuration is a 180° rotation of the third arrayconfiguration with respect to a central location of the first spacer.

In some embodiments of the ion-exchange device, the first spacer meshand the first spacer border are integral, and the second spacer mesh andthe second spacer border are integral.

In some embodiments of the ion-exchange device, the first spacer meshand the first spacer border are separate components, and the secondspacer mesh and the second spacer border are separate components.

In some embodiments, a method of fabricating a spacer for anion-exchange device is provided, the method comprising: masking twosides of a polymer film roll; forming a polymer sheet from the polymerfilm roll; and cutting the polymer sheet using a laser engraver to forma plurality of channels, wherein each channel of the plurality ofchannels comprises a width of 0.005 inches to 0.015 inches.

In some embodiments of the method, cutting the polymer sheet comprisesforming an internal cavity and one or more openings in the polymer sheetto form a spacer border.

In some embodiments of the method, cutting the polymer sheet comprisescutting a spacer border and a spacer mesh integrally.

In some embodiments of the method, the polymer of the polymer film rolland the polymer sheet comprises a stiffness greater than 2.5 GPa.

In some embodiments of the method, the polymer of the polymer film rolland the polymer sheet is polyethylene terephthalate.

In some embodiments of the method, masking two sides of a polymer filmroll comprises applying a low tack paper masking to two sides of apolymer film roll.

In some embodiments of the method, the thickness of the spacer has atolerance of less than 0.002 inches.

In some embodiments of the method, cutting the polymer film sheetcomprises configuring the laser engraver to a laser speed of 30-40inches per second.

In some embodiments of the method, cutting the polymer film sheetcomprises configuring the laser engraver to a power of 40 to 60 Watts.

In some embodiments of the method, cutting the polymer film sheetcomprises configuring the laser engraver to a frequency of 2000 to 3000pulses per inch.

In some embodiments of the method, cutting the polymer film sheetcomprises configuring the laser engraver to a focus of 2 inches+/−0.005inches.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 illustrates a schematic side view of an ion-exchange device,according to some embodiments;

FIG. 2 illustrates an exploded view of the flow channels through anion-exchange device, according to some embodiments;

FIG. 3 illustrates a close-up front view of an ion-exchange device,according to some embodiments;

FIG. 4 illustrates close-up view of a channel of a spacer border,according to some embodiments;

FIG. 5 illustrates a close-up view showing flow channels through anion-exchange device, according to some embodiments;

FIG. 6 illustrates a close-up view of membrane bridging into a channel,according to some embodiments;

FIG. 7 illustrates a form of spacer border deformation, according tosome embodiments;

FIG. 8 illustrates a close-up view of flow distribution throughindividual channels and arrays of channels in a spacer border, accordingto some embodiments; and

FIG. 9 illustrates a process flow chart of a fabrication process for aspacer border, according to some embodiments.

DETAILED DESCRIPTION OF THE DISCLOSURE

Described are spacer borders and ion-exchange devices and methods forfabricating spacer borders for use in an ion-exchange device. Asdescribed above, the performance of an ion-exchange device relies on thedistribution of fluid flow across the ion-exchange membranes of thedevice, as well as the reliability and effectiveness of the internalseals (i.e., seals between adjacent intermembrane chambers) and externalseals (i.e., seals between an interior space and an exterior space ofthe device) of the device. Poor flow distribution decreases thecapacity, production rate, and efficacy of an ion-exchange device. Poorinternal seals introduce leaks and cross-contamination from oneintermembrane chamber to an adjacent intermembrane chamber. Poorexternal seals introduce safety hazards, leaks from an interior of thedevice to an exterior of the device, and contamination from the externalenvironment. Accordingly, embodiments provided herein can improve fluidflow distribution through intermembrane chambers and across ion-exchangemembranes, can improve internal seals along an exterior surface, and canimprove internal seals between adjacent intermembrane chambers of anion-exchange device.

Ion-exchange systems and devices disclosed herein can include at leastone pair of electrodes and at least one pair of ion-exchange membranesplaced there between. The at least one pair of ion-exchange membranescan include a cation-exchange membrane (“CEM”) and an anion-exchangemembrane (“AEM”). In addition, at least one of the ion-exchangemembranes (i.e., CEMs and/or AEMs) has a spacer on the surface of theion-exchange membrane facing the other exchange membrane in anion-exchange device. In some embodiments, both the CEMs and the AEMshave a spacer on at least one surface facing the other ion-exchangemembrane. The spacer can include a spacer border and a spacer mesh.

FIG. 1 shows a schematic side view of ion-exchange system 100 accordingto some embodiments disclosed herein. Ion-exchange system 100 caninclude CEMs 104 and AEMs 106 sandwiched between two electrodes 102. Insome embodiments, one or more CEM 104 and one or more AEM 106 mayalternate throughout a length of the ion-exchange device 100.

An electrode 102 is shown on opposing ends of ion-exchange device 100.One electrode 102 can be a cathode and another electrode 102 can be ananode. In some embodiments, one or more electrodes 102 can encompass oneor more fluid channels for electrolyte stream 112. For example, a fluidchannel for electrolyte stream 112 of electrode 102 can be locatedbetween one or more CEM 104 and an electrode 102, or between one or moreAEM 106 and an electrode 102. Ion-exchange device 100 may also includeone or more fluid channels for influent stream 136. One or more influentstream 136 may be located between a CEM 104 and an AEM 106. Influentstream 136 can comprise water. In some embodiments, water of influentstream 136 may be purified by flowing through one or more intermembranechambers located between two or more alternating CEM 104 and AEM 106.

AEM 106 can allow passage of negatively charged ions and cansubstantially block the passage of positively charged ions. Conversely,CEM 104 can allow the passage of positively charged ions and cansubstantially block the passage of negatively charged ions.

Electrolyte stream 112 may be in direct contact with one or moreelectrodes 102. In some embodiments, electrolyte stream 112 may comprisethe same fluid as the fluid of influent stream 136. In some embodiments,electrolyte stream 112 may comprise a fluid different from the fluid ofinfluent stream 136. For example, electrolyte stream 112 can be any oneor more of a variety of conductive fluids including, but not limited to,raw influent, a separately managed electrolyte fluid, NaCl solution,sodium sulfate solution, or iron chloride solution.

In some embodiments, ion-exchange device 100 can include one or morespacers on at least one surface of a CEM 104 or an AEM 106. In someembodiments, one or more spacer may be located on two opposing surfacesof a CEM 104 and/or an AEM 106. Further, ion-exchange device 100 mayinclude one or more spacers between any two adjacent ion-exchangemembranes (i.e., between an AEM 106 and a CEM 104). The region formedbetween any two adjacent ion-exchange membranes by one or more spacersforms an intermembrane chamber.

When an electric charge is applied to one or more electrodes 102 ofion-exchange device 100, the ions of influent stream 136 flowing throughan intermembrane chamber between any two ion-exchange membranes (i.e.,one or more CEM 104 and one or more AEM 106) can migrate towards theelectrode of opposite charge. Specifically, ion-exchange membranescomprise ionically conductive pores having either a positive or anegative charge. These pores are permselective, meaning that theyselectively permeate ions of an opposite charge. Thus, the alternatingarrangement of the ion-exchange membranes can generate alternatingintermembrane chambers comprising decreasing ionic concentration andcomprising increasing ionic concentration as the ions migrate towardsthe oppositely-charged electrode 102.

An intermembrane chamber can be formed from a spacer border and a spacermesh and creates a path for fluids to flow. The number of intermembranechambers may be increased by introducing additional alternating pairs ofion-exchange membranes. Introducing additional alternating pairs of CEMs104 and AEMs 106 (and the intermembrane chambers formed between eachpair of ion-exchange membranes) can also increase the capacity ofion-exchange device 100. In addition, the functioning ability of anindividual ion-exchange cell (i.e., a single CEM 104 paired with asingle AEM 106 to form a single intermembrane chamber) can be greatlyaugmented by configuring ion-exchange cells into ion-exchange stacks(i.e., a series of multiple ion-exchange cells.)

As described above, ions of influent stream 136 flowing through anintermembrane chamber can migrate towards electrode 102 of oppositecharge when an electric current is applied to ion-exchange device 100.This separation mechanism can separate influent stream 136 into twodifferent streams of opposite ionic charge. For example, when used fordesalination, influent stream 136 may be separated into brine stream 108and product stream 110. Brine stream 108 is generally a waste stream. Insome embodiments, product stream 110 may have a lower ionicconcentration than brine stream 108.

In some embodiments, product stream 110 may have a predeterminedtreatment level. For example, ion-exchange system 100 may be configuredto remove several types of ions (e.g., monovalent ions, divalent ions,etc.) or it may be configured to remove a specific type of ion (e.g.,arsenic, fluoride, perchlorate, lithium, gold, silver, etc.). Further,ion-exchange system 100 can be held together using a compression systemthat comprises using two compression plates on opposite ends of thedevice. In some embodiments, a single pair of compression plates may beused (i.e., one on either end of the outside of the stack) to achieve aworking, reliable seal.

To create intermembrane chambers between two ion-exchange membranes,spacers can be inserted between the ion-exchange membranes. FIG. 2illustrates an exploded view of a portion of an ion-exchange device 200that includes three ion-exchange membranes (two CEMs 204 and one AEM206), two spacer meshes 216, and two spacer borders 214. The fluid flowpath through these components is also shown (i.e., product flow path 222a, brine flow path 222 b, product outlet 224 a and brine outlet 224 b).

In FIG. 2, stacking arrangement of ion-exchange membranes and spacers(including spacer borders 214 and spacer meshes 216) is shownsequentially as CEM 204, spacer mesh 216 and spacer border 214, AEM 206,spacer mesh 216 and spacer border 214, and CEM 204. Pairs ofion-exchange membranes require separation (in the form an intermembranechamber) to allow fluid to flow between them. Typically, anon-conductive spacer mesh 216 and spacer border 214 pair can providethe separation between the membrane pairs, forming an intermembranechamber. In some embodiments, spacer border 214 and spacer mesh 216 maybe separate components. In some embodiments, spacer border 214 andspacer mesh 216 may be integrated as a single component. In actual use,the ion-exchange membranes and spacer border/spacer meshes can besandwiched together such that spacer border 214 can seal against theion-exchange membranes and provide contained intermembrane chambers.Fluid can pass through the intermembrane chambers for treatment.

When these components are sandwiched together as described above,openings 218 located along a top edge and a lower edge of each spacerborder 214 (with respect to FIG. 2) can create inlet and outletopenings. As shown in FIG. 2, openings 218 include at least two productwater inlet openings 242 a, at least two brine water inlet openings 242b, at least two brine water outlet openings 242 c, and at least twoproduct water outlet openings 242 d. A large internal cavity 238 ofspacer border 214 can include a spacer mesh 216 used to maintainseparation between membranes in the ion-exchange system 200. Inaddition, spacers (i.e., spacer border 214 and spacer mesh 216) canprovide torturous paths for the fluid to flow. This increased turbulencecan increase the flow distribution through the intermembrane chamber,increasing the performance and effectiveness of ion-exchange device 200.

In addition to openings 218, each spacer border 214 can also include aseries of channels 220. Channels 220 can be etched into spacer border214 according to specific dimensions and/or a specific orientation toachieve a particular outcome. For example, in some embodiments, channels220 may be configured to distribute water flow maximally across thesurface area of spacer mesh 214.

In some embodiments, as shown in FIG. 2, the inlet of product flow paths222 a and brine flow paths 222 b alternate based upon the location oftheir inlet openings (i.e., product water inlet openings 242 a and brinewater inlet openings 242 b). In some embodiments, channels 220 areetched into spacer border 214 to direct fluid to internal cavity 238 andto increase fluid distribution across spacer mesh 216 and theintermembrane chamber corresponding to that specific spacer border 214and spacer mesh 216.

The specific orientation of a plurality of channels 220 may also impactthe performance of ion-exchange device 200. For example, channels 220 ofFIG. 2 are shown in an “array” configuration. Otherorientations/configurations may include rectangles, straight lines,triangles, or any other suitable configuration. In addition, channels220 may be straight, as shown in FIG. 2, or they may comprise curvesand/or angles/corners. In some embodiments, a plurality of narrowchannels 220 may converge, forming a single wide channel 220, or asingle wide channel 220 may divide into a plurality of narrow channels220. In some embodiments, the width of one or more channels 220 maychange along a length of the channel. For example, one or more channels220 may expand to comprise a greater width as the channel 220 approachesthe intermembrane chamber. In some embodiments, one or more channels 220may converge to a smaller width as the channel 220 approaches theintermembrane chamber.

Each membrane (i.e., CEM 204 and AEM 206) can include one or moreopenings which, when combined with one or more spacer border 216, createone or more opening 218 along a length of the ion-exchange device 200.The one or more opening 218 and the geometry of the spacer border 214and spacer mesh 216 can allow fluids to flow into channels 220 andacross the contained area created by the spacer border. For example, inFIG. 2, fluid can be introduced at inlet opening along a bottom ofion-exchange device 200 (with respect to FIG. 2). The fluid can flow upalong channels 220 of a spacer border 216, across a spacer mesh 214,through channels 220 of a spacer border 216, and to one or more outletopening 218 at a top of ion-exchange device 200.

As shown in FIG. 2 and described above, openings 218 along a bottom ofion-exchange device 200 (with respect to FIG. 2) alternate betweenproduct water inlet openings 242 a and brine water inlet openings 242 b.Openings 218 along a top of ion-exchange device 200 (with respect toFIG. 2) alternate between product water outlet openings 242 d and brinewater outlet openings 242 c. Further, as shown by the arrows, the fluidflows diagonally across spacer mesh 216 and the intermembrane chambercorresponding to that particular spacer mesh 216. Thus, the outletopenings (i.e., brine water outlet openings 242 c and product wateroutlet openings 242 d) are located diagonally across spacer mesh 216from the respective inlet openings (i.e., brine water inlet openings 242b and product water inlet openings 242 a). In some embodiments, thisparticular flow pattern may help maximize fluid distribution across amembrane surface.

However, the configuration of openings 218 and the flow path acrossspacer mesh 216 may take different forms. Unlike the alternatingopenings 218 discussed above, product water inlet openings 242 a may begrouped together and brine water inlet openings 242 b may be groupedtogether. In some embodiments, the outlet openings (i.e., brine wateroutlet openings 242 c and product water outlet openings 242 d) may notbe located diagonally across the spacer mesh 216 from the respectiveinlet openings (i.e., brine water inlet openings 242 b and product waterinlet openings 242 a) to generate a diagonal fluid flow across spacermesh 216, as described above. Instead, one or more of the product flowpath 222 a and brine flow path 222 b may be directed to flow directlyacross in a horizontal or vertical direction across spacer mesh 216. Asshown in FIG. 2, inlet openings are positioned along a bottom ofion-exchange device 200 and outlet openings are positioned along a topof ion-exchange device 200. In some embodiments, inlet openings may belocated along a top of ion-exchange device 200, and outlet openings maybe located along a bottom of ion-exchange device. In some embodiments,openings may be located along a left or a right side of ion-exchangedevice 200. Other suitable configurations of openings and flow pathsacross spacer mesh 216 are readily conceivable by one having ordinaryskill in the art.

FIG. 3 demonstrates a close-up front view of a portion of a spacer stack300 comprising a plurality of spacer borders 314 and a plurality ofspacer meshes 316. In particular, FIG. 3 shows a stack of spacersconfigured to distribute fluid to at least two separate intermembranechambers using openings 318 of at least two different sizes and/orshapes and a series of channels 320 etched in each spacer border 314. Insome embodiments, a spacer of spacer stack 300 may comprise a spacerborder 314, an internal cavity 338, a spacer mesh 316, channels 320, oneor more configurations 326 comprising one or more channels 320, and twoor more openings 318.

Like channels 220 of FIG. 2, channels 320 of FIG. 3 are etched in anarray configuration 326. In particular, one or more array configuration326 is comprised of narrow flow channels extending from internal cavity338 towards opening 318. FIG. 3 illustrates the relationship between anarray 326 of channels 320 of a first spacer border 314 and an array 326of channels 320 of a second spacer border 314. In the configurationshown, one or more channel 320 of each array 326 of a first spacerborder 314 (e.g., a topmost spacer border) overlaps with one or morechannels 320 of an array 326 of a second spacer border 314 (e.g., anunderlying spacer border). This overlapping configuration can encourageand improve water distribution across the intermembrane chamber.

As shown, channels 320 of FIG. 3 are etched in the configuration of anarray 326. However, other configurations may be generated, such asrectangles, straight lines, triangles, or any other suitableconfiguration. In addition, channels 320 may be straight, as shown inFIG. 3, or they may comprise curves and/or angles/corners. In someembodiments, a plurality of narrow channels 320 may converge, forming asingle wide channel 320, or a single wide channel 320 may divide into aplurality of narrow channels 320. Channels 320 can also be etched suchthat each one is approximately equal in length. Having a plurality ofchannels 320 that are approximately equal in length may allow an equalpressure drop across each channel. However, some suitable configurationsmay allow for channels 320 of various lengths.

FIG. 3 also shows the configuration of openings 318 when two or morespacers are stacked together. The heavy lines of FIG. 3 representfeatures of the topmost spacer and/or features of an underlying spacerthat are visible through openings of the topmost spacer. The lighterlines represent features of the underlying spacer that are covered bythe topmost spacer and/or not visible through an opening of the topmostspacer. Each smaller square-shaped opening 318 comprises a channel array326 extending from the internal cavity towards the opening. Fluiddirected through these square-shaped openings can enter channel array326 and be transported across spacer mesh 316 and correspondingintermembrane chamber. Each larger rectangular-shaped opening 318exposes a portion of a channel array 326 of an underlying spacer. Fluiddirected through these openings can pass through the rectangular-shapedopening of a first spacer (e.g., the topmost spacer) and to the channelarray 326 of a second spacer (e.g., an underlying spacer). From there,the fluid may be transported through channels 320 of array 326 andacross spacer mesh 316 and the accompanying intermembrane chamber of thesecond spacer.

Spacer borders 314 and openings 318 can be of various geometries and arenot limited to the geometries described herein and/or represented in thefigures. For example, circles, diamonds, or combinations of numerousshapes may be used for either feature. Furthermore, openings 318 can bespaced further apart or closer together depending on the fluid treatmentspecifications. In some embodiments, the size and/or shape of openings318 may vary and/or alternate on a single spacer border 314. Forexample, on the topmost spacer border 314, from left to right is alarger rectangular opening, a smaller square opening, a largerrectangular opening, and a smaller square opening. In some embodiments,openings 318 may alternate in size from one spacer to the next in astack of spacers. For example, topmost spacer border 314 comprises alarger, rectangular-shaped opening 318 positioned at a far left side ofspacer border 314. In a stack of spacers, the shapes of each openingthat align with this particular rectangular-shaped opening 318 when aplurality of spacers (and optionally ion-exchange membranes) are stackedtogether may alternate from one spacer to the next.

FIG. 4 provides a close-up view of channels 420 of a spacer 400. Inparticular, FIG. 4 indicates specific dimensions that may be consideredduring design and fabrication of spacer 400 and may directly impact theexternal sealing capabilities, internal sealing capabilities, and/orflow distribution across an intermembrane chamber.

The thickness of the ion-exchange membranes (i.e., CEMs and AEMs) of anion-exchange device may impact the risk of membrane bridging (describedbelow with respect to FIG. 6) and internal leaking. For example, arelatively thick ion-exchange membrane may extrude into one or morechannels 420 and effectively block fluid flow. Further, due tocompressive forces placed on the ion-exchange membrane stack in anion-exchange device, relatively thinner ion-exchange membranes may havea tendency to form channels on a side of the ion-exchange membraneopposite channels 420, allowing fluid from an adjacent intermembranechamber to leak into the affected intermembrane chamber. Thus, tominimize these adverse effects, it has been determined that thethickness of the ion-exchange membrane layers may be from 0.001 inchesto 0.030 inches. In some embodiments, the thickness of the ion-exchangemembrane layer may be from 0.001 inches to 0.020 inches, from 0.001inches to 0.015 inches, or from 0.001 inches to 0.010 inches. In someembodiments, the thickness of the ion-exchange membrane layer may begreater than 0.001 inches, greater than 0.003 inches, greater than 0.005inches, greater than 0.010 inches, greater than 0.015 inches, greaterthan 0.020 inches, or greater than 0.025 inches. In some embodiments,the thickness of the ion-exchange membrane layers may be less than 0.030inches, less than 0.025 inches, less than 0.020 inches, less than 0.015inches, less than 0.010 inches, less than 0.008 inches, less than 0.005inches, or less than 0.003 inches.

Spacer border 414 well-suited for sealing ion-exchange membranesdescribed above may comprise a thickness of 0.001 inches to 0.050inches. In some embodiments, spacer border 414 may comprise a thicknessfrom 0.003 inches to 0.040 inches, from 0.005 inches to 0.030 inches, orfrom 0.006 inches to 0.010 inches. In some embodiments, spacer border414 may comprise a thickness less than 0.050 inches, less than 0.040inches, less than 0.030 inches, less than 0.020 inches, less than 0.010inches, less than 0.008 inches, less than 0.006 inches, less than 0.005inches, less than 0.003 inches, or less than 0.002 inches. In someembodiments, spacer border 414 may comprise a thickness greater than0.001 inches, greater than 0.003 inches, greater than 0.005 inches,greater than 0.007 inches, greater than 0.009 inches, greater than 0.010inches, greater than 0.020 inches, greater than 0.030 inches, or greaterthan 0.040 inches.

As mentioned above, channels 420 may be etched into spacer border 414according to specific dimensions and/or a specific orientation. Forexample, the width of an individual chamber 420 and any difference inwidth from a first channel 420 to a second channel 420 can be criticalto performance of ion-exchange device 420. In some embodiments, achannel 420 width from 0.001 inches to 0.020 inches or 0.005 inches to0.015 inches may be used, particularly for a fluid having a conductivityof <10,000 μS/cm or <5,000 μS/cm. A channel 420 having a width accordingto these dimensions can result in better flow distribution, which canlead to a lower overall electrical resistance. In some embodiments, achannel 420 width may be less than 0.020 inches, less than 0.015 inches,less than 0.012 inches, less than 0.010 inches, less than 0.008 inches,less than 0.005 inches, or less than 0.003 inches. In some embodiments,a channel 420 width may be greater than 0.001 inches, greater than 0.003inches, greater than 0.005 inches, greater than 0.008 inches, greaterthan 0.010 inches, greater than 0.012 inches, or greater than 0.015inches. Ideally, any variation in channel cutting should be less than0.002 inches. As described in more detail below, a laser cutting andmasking procedure can be used to ensure these precise cuts.

FIG. 5 provides a closer look at the flow pattern through stack 500. Insome embodiments, stack 500 may comprise a plurality of alternating CEMsand AEMs, each separated by one or more spacers (i.e., spacer border 514and spacer mesh 516). Specifically, FIG. 5 illustrates a fluid flow pathas it travels from inlet openings 518 to an intermembrane chamber. Insome embodiments, fluid flows through inlet openings 518 to an array 526of channels 520 and across spacer mesh 516 of an intermembrane chamber.In FIG. 5, fluid is shown entering from a rear side of stack 500.Specifically, fluid inlet stream 522 enters through a large rectangularopening 518 of a first spacer border 514 along a rear side of stack 500.Fluid stream 522 passes through this first rectangular opening 518 andto channels 520 of channel array 526 of a second spacer 514. Channels520 transport fluid of fluid stream 522 across a length of channels 520of array 526 to a spacer mesh 516. The fluid of fluid stream 522 thentravels across spacer mesh 516 and the intermembrane chambercorresponding to the second spacer border 514.

FIG. 6 shows a close-up view of spacer 600. In particular, membranebridging is occurring in spacer 600. Membrane bridging in an example ofan internal leak that can occur when a leak path (e.g. leak path 630) iscreated by the membrane in between narrow channels 620. Membranebridging can cause cross-contamination of fluid from one intermembranechamber to an adjacent intermembrane chamber in addition to other poorperformance characteristics of an ion-exchange device. The severity ofmembrane bridging can depend on the material of the spacer 600 and/orthe thickness of channels 620. However, some membrane bridging may occurwithout producing any catastrophic effects on the performance of anion-exchange device according to some embodiments described herein.These are discussed in detail below, particularly with respect to FIG.7.

In some embodiments, spacer border 614 may be fabricated from a singlepolymer sheet. In some embodiments, both spacer border 614 and spacermesh 616 may be fabricated as a single component from a single polymersheet. The polymer used to fabricate spacer border 614 and/or spacermesh 616 may include polyethylene terephthalate (PET), polyethylene,ethylene propylene diene terpolymer (EDPM), elastomeric materials, orany other suitable materials.

FIG. 7 illustrates possible deformation of spacer border 714 that canoccur in some embodiments. In particular, compressive forces required toeffectively seal a stack of spacers and ion-exchange membranes in anion-exchange device can cause material of spacer border 714 to bulge orflow into channel 720 itself, creating an obstruction within channel720. Obstructions caused by the deformation will increase the flowresistance in channel 720 and can possibly cut off flow through channel720 entirely.

For example, low modulus plastics (i.e., polyethylene and elastomericmaterials such as EPDM and neoprene) are susceptible to this type ofdeformation and thus may not be ideal materials to use in someembodiments. If used, spacer borders fabricated of these low modulusplastics may be prepared with relatively wide channels (e.g., greaterthan 0.020 inches). In some embodiments, spacer borders of thesematerials may utilize a mesh or insert to bridge channel and seal theadjacent ion-exchange membranes.

On the other hand, polyethylene terephthalate (PET) film and otherplastics comprising a stiffness of greater than 2.5 GPa can resistdeformation more effectively than the low modulus plastics describedabove. Thus, thinner channels may be etched into the spacer border filmwithout forming large obstructions under compression. Additionally, PETfilms are typically rigid enough to maintain the channel geometry duringmanufacturing, whereas less rigid materials may be more susceptible todamage or deformation causing the channel gaps to vary or move duringassembly. These materials having a lower rigidity may result ininconsistent channel geometry and poor sealing as the line of forcethrough the stack may be broken. More detail of spacer borderfabrication techniques are provided below.

FIG. 8 illustrates fluid flow path of a single intermembrane chamber 800according to some embodiments. Intermembrane chamber 800 comprisesspacer border 814 and internal cavity 838. Spacer border 814 includesone or more openings 818, one or more channels 820, and one or morechannel array 826. As shown, when fluid enters a channel 820 at alocation proximate to opening 818 corresponding to said channel 820, thefluid travels along a length of channel 820 until it reaches internalcavity 838. As shown in FIG. 8, a plurality of channels 820 is etchedinto the configuration of an array (i.e., array 826).

However, as discussed above, other configurations of channels 820 mayalso be reasonably used (i.e., rectangles, straight lines, triangles,etc.). In addition, channels 820 may be straight, as shown in FIG. 8, orthey may comprise curves and/or angles/corners. In some embodiments, aplurality of narrow channels 820 may converge, forming a single widechannel 820, or a single wide channel 820 may divide into a plurality ofnarrow channels 820. Channels 820 can also be etched such that each oneis approximately equal in length. Having a plurality of channels 820that are approximately equal in length may allow an equal pressure dropacross each channel. However, some suitable configurations may allow forchannels 820 of various lengths.

The arrows shown in FIG. 8 illustrate a flow path of fluid as the fluidexits plurality of channels 820. Orienting channels 820 into one or morearray configuration 826 allows for increased flow distribution acrossinternal cavity 838 and the intermembrane channel formed from spacerborder 814 and internal cavity 838, as indicated by the arrows provided.However, as discussed above, other configurations of channels 820 may bereasonably used as well.

Fabricating Spacer Borders for Use in Ion-Exchange Membrane

FIG. 9 provides a process flow chart for a method 900 of fabricatingspacers (i.e., spacer border and/or spacer mesh) according to someembodiments herein. In some embodiments, a thin spacer border may becreated from single component and provide all the benefits state abovethrough a combination of spacer material, membrane material, and spacergeometry.

In step 902 of process 900, a low tack paper masking (e.g., paper backtape) is applied to both sides of a polymer film roll. Unlike a low tackpaper back tape, a plastic back tape may fuse with the PET during lasercutting. Without a mask, the laser of the CNC laser engraver may locallymelt the PET material in the region of the channels and cause thematerial being removed to fuse with the spacer border. This fusioncreates an increased thickness of the spacer border in the region of thechannel(s). Accordingly, to keep the material thickness variation toless than 0.002 inches, tape can be applied to both sides of the PETfilm. A single side of the PET roll may be masked, but the repeatabilityof the cutting process may suffer. As described above, the film used mayinclude any suitable material such as PET, polyethylene, ethylenepropylene diene terpolymer (EDPM), elastomeric materials, etc.

In some embodiments, the spacer border is composed of PET (i.e.,polyethylene terephthalate). PET is a versatile plastic and compared toother conventional spacer materials, has a relatively high elasticmodulus (3.5 GPa). PET also has a unique combination of relatively highstiffness while also having the ability to be molded into shapes withdimensions having tight tolerances. For example, stacks for anion-exchange device can have a thickness tolerance of +/−0.0001 inchesto form a reliable sealing surface. Variations in film thickness of muchgreater than 0.0001 inches can lead to problems including misalignment,leaking, increases in pressure drop, changing the flow pattern ofadjacent layers, etc. Accordingly, other high modulus plastics (i.e.,materials having a Young's modulus of greater than 2.5 GPa) may also beconsidered, but few materials have the unique combination of propertiescharacteristic of PET.

In step 904, a PET roll is converted into a PET sheet in preparation forcutting and/or engraving. Specifically, the PET roll is cut into sheetsin preparation for loading into a CNC laser engraver. Alternatively, aroll-fed laser engraver may be used, and the masking tape may be appliedin a separate step, before the laser engraver.

In step 906 of process 900, the engraving machine is prepared to cut thePET film. In some embodiments, a laser engraving machine may be used tocut the film. In particular, process parameters such as the laser speed,power, frequency, and focus may be adjusted. The process parametersshould be optimized such that the machine can cut the PET film withminimal melting outside of the region of the cut and such that themachine can cut the film in a single pass.

In some embodiments, the laser speed may be from 20 to 50 inches/second.In some embodiments, the laser speed may be from 30 to 40 inches/second.In some embodiments, the laser speed may be less than 50 inches/second,less than 40 inches/second, or less than 30 inches/second.

In some embodiments, the power of the machine may be from 30 to 80Watts. In some embodiments, the machine may be powered at 40 to 60Watts. In some embodiments, the machine may be powered at less than 80watts, less than 70 Watts, less than 60 Watts, less than 50 Watts, orless than 40 Watts. In some embodiments, the machine may be powered atmore than 30 Watts, more than 40 Watts, more than 50 Watts, more than 60Watts, or more than 70 Watts.

In some embodiments, the frequency of the machine may be from 1000 to4000 pulses per inch. In some embodiments, the frequency of the machinemay be from 2000 to 3000 pulses per inch. In some embodiments, thefrequency may be more than 1000, more than 1050, more than 2000, morethan 2050, more than 3000, or more than 3050 pulses per inch. In someembodiments, the frequency of the machine may be less than 4000, lessthan 3050, less than 3000, less than 2050, less than 2000, or less than1050 pulses per inch.

In some embodiments, the focus of the machine may be from 1 inch to 4inches with a tolerance of +/−0.005 inches. In some embodiments, thefocus of the machine may be from 2 inches to 3 inches with a toleranceof +/−0.005 inches. In some embodiments, the focus of the machine may beless than 4 inches, less than 3.5 inches, less than 3 inches, less than2.5 inches, less than 2 inches, or less than 1.5 inches with a toleranceof +/−0.005 inches. In some embodiments, the focus of the machine may bemore than 1 inches, more than 1.5 inches, more than 2 inches, more than2.5 inches, more than 3 inches, or more than 3.5 inches with a toleranceof +/−0.005 inches.

In some embodiments, a CNC laser engraver is used to ensure the tighttolerances necessary when preparing stack components of an ion-exchangedevice. For example, an Epilog Fusion M2 40 (Epilog Laser) may be used.Other suitable laser cutting/engraving machines may be used as well.However, other cutting, engraving, and/or etching processes, such as diecutting and other mechanical methods, may not be desirable for creatingclean, deformation-free patterns in the polymer film (i.e., PET film).

In step 908, positive air pressure is applied to a laser head of the CNClaser engraver (in the region of the cut), and negative air pressure isapplied to a supporting table of the CNC laser engraver in preparationfor etching. This air pressure balance can help remove the cut piecesaway from the region of the cutting to prevent them from melting andfusing back to the PET film from which they were removed.

In step 910, after the cutting is complete, the mask may be removed. Thecut spacer border may optionally be placed in a mixture of soap andwater to assist in the removal of the mask and remove any remainingdebris from the channels.

The preceding description sets forth exemplary methods, parameters andthe like. It should be recognized, however, that such description is notintended as a limitation on the scope of the present disclosure but isinstead provided as a description of exemplary embodiments. Theillustrative embodiments described above are not meant to be exhaustiveor to limit the disclosure to the precise forms disclosed. Manymodifications and variations are possible in view of the aboveteachings. The embodiments were chosen and described to best explain theprinciples of the disclosed techniques and their practical applications.Others skilled in the art are thereby enabled to best utilize thetechniques, and various embodiments with various modifications as aresuited to the particular use contemplated.

Although the disclosure and examples have been thoroughly described withreference to the accompanying figures, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of the disclosure and examples as defined bythe claims. In the preceding description of the disclosure andembodiments, reference is made to the accompanying drawings, in whichare shown, by way of illustration, specific embodiments that can bepracticed. It is to be understood that other embodiments and examplescan be practiced, and changes can be made without departing from thescope of the present disclosure.

Although the preceding description uses terms first, second, etc. todescribe various elements, these elements should not be limited by theterms. These terms are only used to distinguish one element fromanother.

Also, it is also to be understood that the singular forms “a,” “an,” and“the” used in the preceding description are intended to include theplural forms as well unless the context indicates otherwise. It is alsoto be understood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items. It is further to be understood that the terms“includes, “including,” “comprises,” and/or “comprising,” when usedherein, specify the presence of stated features, integers, steps,operations, elements, components, and/or units but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, units, and/or groups thereof.

The term “if” may be construed to mean “when” or “upon” or “in responseto determining” or “in response to detecting,” depending on the context.

Although the disclosure and examples have been fully described withreference to the accompanying figures, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of the disclosure and examples as defined bythe claims.

1. A spacer for an ion-exchange device comprising: a spacer mesh; and aspacer border comprising: an internal cavity surrounded by a perimeterof the spacer border; a first inlet opening and a second inlet openingwithin the perimeter of the spacer border, wherein the first inletopening and the second inlet opening are located on adjacent sides ofthe internal cavity; and a plurality of channels located within theperimeter and between the first inlet opening and the internal cavity,wherein each channel of the first plurality of channels extends from theinternal cavity towards the first inlet opening, wherein a total area ofthe first inlet opening is different than a total area of the secondinlet opening.
 2. The spacer of claim 1, wherein the spacer bordercomprises a polymer having a stiffness greater than 2.5 GPa.
 3. Thespacer of claim 1, wherein the spacer border comprises polyethyleneterephthalate.
 4. The spacer of claim 1, wherein each channel of theplurality of channels comprises a width from 0.005 inches to 0.015inches.
 5. The spacer of claim 1, wherein the plurality of channels isoriented in a first array configuration.
 6. The spacer of claim 1,comprising a thickness of 0.003 inches to 0.020 inches.
 7. The spacer ofclaim 1, comprising a thickness of 0.003 inches to 0.010 inches.
 8. Thespacer of claim 1, wherein an end of each channel of the plurality ofchannels opens into the internal cavity.
 9. The spacer of claim 1,wherein the spacer mesh and the spacer border are integral.
 10. Thespacer of claim 1, wherein the spacer mesh and the spacer border areseparate components.